From experience, the derivative part can improve regulation during load sharing, power regulation and static synchronisation, when
the parameter is properly tuned.
INFO
Set
Td
to zero to turn off the derivative part.
INFO
Use the derivative part if the situation requires very precise regulation (for example, static synchronisation). If the derivative
part is used, it MUST be properly tuned.
Tuning the controller PID
You can tune each of the PID parts to optimise the controller regulation for your system.
More information
See
Tune regulators, Analogue controlled regulators, Tuning PID regulators
in the
Commissioning guidelines
for
more information.
6.1.3 Relay regulation
Relay control activates or deactivates the
[Regulator] increase
and
[Regulator] decrease
relays to increase or decrease the control
signal, based on the output of the controller (where [Regulator] is either GOV, or AVR).
Configuring digital outputs
To use relay outputs to communicate with the governor or AVR, assign the digital output regulation functions under
Configure >
Input/output
.
Set the parameter
Configure > Parameters > Regulators > [Regulator] general configuration > Output type
to
Relay
(where
[Regulator]
is
Governor
or
AVR
).
Relay regulation ranges
The controller determines whether the output should be increased or decreased by comparing the measured value to the set point.
The controller determines how far the deviation (also known as the error) is from the set point, and selects an output range. The
output can be in one of three ranges, which are summarised in the table below:
Table 6.1
Relay regulation ranges
Range
Relay position Notes
Constant
range
Closed or
intermittent
open/close
The measured value is far away from the reference value. The
[Regulator] increase
* or
[Regulator]
decrease
* relay is activated for the maximum time allowed by the
Period time
and the
Maximum
ON time
percentage. If the measured value is still far away after the maximum time was reached,
then the relay is reactivated after the
Period time
is reached.
See point 1 on the figures below for an example where the
Maximum ON time
is set to 100 %.
Variable
range
Intermittent
open/close
The measured value is approaching the reference value, but is not in the deadband range yet. The
[Regulator] increase*
or
[Regulator] decrease*
relay pulses. The signal from the relay is thus
intermittent.
The length of the pulse is dependent on the distance from the reference value, the period time and
the controller gain,
Kp
. If the measured value is further away from the reference value, the
controller uses a longer pulse. If the measured value is closer to the reference value, the controller
uses a shorter pulse. You can define the minimum pulse width.
See points 2, 3, 4 and 5 on the figures below.
Deadband
range
Open
The measured value is so close to the reference value that it is within the deadband percentage of
the reference value. The deadband is specific to the control type that is active, and you can define
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